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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

Eng Refresh + LMA, etc 57

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Based on the VIN, this NSX left the factory with 1st gen. ABS.
However, it has 2nd gen. one so the owner is very lucky as it has much better protection against the leaky solenoid issue that many 1st gen. ABS users are suffering from.

Still, if you don’t exercise your ABS regularly, you will end up with leaky solenoid issue as well as the stuck closed solenoid.

Cleaned the reservoir first in preparation for flushing the accumulator.













So muchy air trapped in the accumulator.

I had to drain the ABS SST four times before I can release all of the pressure.
I always see lots of air in the accumulator but not many systems showed this level of air.
Probably never flushed in the past.











The owner told me that he has never exercised the ABS during his ownership……
He heard ABS pump activated whenever he took the car out for spin but never had ABS warning light.



Many owners think that this would be a good sign of healthy classic ABS…..
I’m afraid not........












And my concern became the reality.

3 out of 4 solenoids were completely stuck closed.
This means that only one wheel (Message to the owner: only the Front Right wheel has operational ABS)
has ABS control so it’s the equivalent of no ABS at all.




There is a special know-how to unblock these stuck closed solenoid but no matter how many times I tired, none of them improved.

Later, during the test driving session, I applied hard braking many times while the tyre was cold from about 10mph but always locked up and
when I got back, tested the bad 3 solenoids but still no changes.

I had similar situation on another NSX and for this, I asked the owner to exercise the ABS every day for about a week and then come back to my place
to check the stuck closed solenoids.
This trick worked so I hope the owner will do the same but probably require much longer exercising days.












Comments

  1. nikey22's Avatar
    Kaz,

    when you mention that 3 out of 4 solenoids were stuck closed, how did you know this? What was the behaviour of the solenoids during you testing that confirmed they were stuck?
    I'm familiar with the flushing procedure in the Dan-o-Land guide, but unable to ascertain which solenoids are truly working well vs. stuck.
  2. Kaz-kzukNA1's Avatar
    Hi, nikey22.
    Probably you are trying to figure out what's happening with your ABS as in your post on NSX Prime.
    I may post something if I can find extra spare time.
    The classic ABS is famous for its leaky solenoid issue (there are two valves at each solenoid but inlet valve is the one causing headache) but there are two modes for it (internal and external).
    I'll leave it for now as it's not related to your question.

    As same as being leaky, it can go the other way round.
    It can seize in closed position, i.e., stuck closed.

    When you apply 12V to the inlet valve, normally, you would see high pressure fluid returning to the reservoir in the form of millions of tiny bubbles.

    However, with stuck closed inlet valve, nothing happens.
    You just hear the solenoid click when 12V was applied but no fluid returning, as if no high pressure fluid left inside the accumulator.

    This is worse than the leaky solenoid because the corner with the stuck closed inlet valve won't have ABS function and simply lock the wheel while at other corners, ABS may operate fine resulting in upsetting the chassis behaviour under braking.
    You won't get any ABS warning light at all for this failure mode because there is no feedback loop of the solenoid operation.

    From what you wrote, your issue is more of leaky solenoid, too much air trapped inside the accumulator or pin hole of the accumulator bladder.
    When you activated each solenoid, did the fluid stop returning to the reservoir immediately/instantly when swithced off the solenoid?

    It's hard to advise without showing exactly what you should look for (I don't have video of this) so I hope you can get the idea.
    It also depends on how leaky it is (super leaky, very leaky, moderate, tiny bit, etc) but on leaky solenoid, you will see fluid still returning to the reservoir even after you switched off the solenoid for another 0.1 - 0.5sec. The time window is not measured but just for you to get the feeling.

    With perfect solenoid, you will see the fluid flow stopping instantly.


    Kaz